1. Field of the Invention
The present invention relates to stringed instruments which include a neck and fingerboard extending the supported strings away from the body of the instrument. More particularly, the present invention relates to an accessory neck having a self-contained internal adjustment mechanism which is accessible from the fingerboard and further operable to adjust the neck independent of the neck being attached to the instrument body.
2. Prior Art
It is often desirable to adjust neck members in typical stringed instruments, such as guitars, in lateral and/or rotational directions. It is known to place a rigid adjustment bar within an enclosed channel in the neck, and selectively move the bar in lateral directions with an adjustment screw which is engaged within a female-threaded opening in one end of the bar. The adjustment screw is typically accessible through a hole in the back of the neck, which is reached by drilling a hole in the back of the guitar. Accessory neck members have been developed to incorporate such adjustment mechanisms and which are interchangeably attachable to different guitar bodies.
One of the motivating factors behind the development of accessory neck members was that the resulting guitar look as much like a conventional electric guitar as possible. Indeed, it is very difficult to get a performer to experiment with new instrument configurations. Musicians tend to hold to traditional designs which they know and trust. Accordingly, the adjustment mechanisms applied to conventional guitars either have been accessible from the ends of the neck or at the back of the guitar. This preserves traditional appearance.
As an example of long-time, traditional practice, the fingerboard has always been a continuous surface, free of holes or adjustment structure, and interrupted only by inlaid frets. It is doubtful that anyone has even considered disturbing the fingerboard with access holes or adjustment structure. Not only is it inconsistent with tradition, but is suggestion sounds impractical as a possible interference with performers' fingers. Further, the practices of the guitar industry have operated to bolster the feeling that the fretboard should be undisturbed and thus free from any adjustment apparatus or access ports therefore. This is clearly demonstrated by observation of the new guitar models that enter the market yearly without departing from this tradition. Accordingly, the accessory neck members remain adjustable only from the back and/or from the ends of the neck.
This is not to say that technical problems have been fully resolved by conventional design criteria. Adjusting the neck on stringed instruments such as guitars and banjos for example, and maintaining proper neck alignment, has been a challenge because a significant amount of force is continuously applied to the neck by a plurality of strings in tension. The spacing between the fingerboard and the strings must be consistent along the length of the neck. Such positioning is even more critical where frets are inlaid in the fingerboard to enable pitch selection of any selected string by depressing one or more fingers on a distal side of the fret from the resonating chamber or pickup part associated with the body of the stringed instrument. Although reference hereafter shall be made to an electric guitar, it will be apparent to those skilled in the art that the principles of this invention could be applied to other stringed instruments which share common construction design. Accordingly, further reference to the specific stringed instrument categorized as a guitar should be deemed to include other stringed instruments of comparable structure.
Proper alignment of the fingerboard of a guitar with respect to the suspended strings is essential. Although spacing and height displacement of strings from the fingerboard can be partially adjusted by the use of a specifically configured bridge or nut, it is preferred that the fingerboard of a guitar be straight and generally flat (meaning nontwisted) so that initial adjustments of the fingerboard position with respect to the rest of the instrument can be made in a predictable and controlled manner, remaining uniform for all frets along the fingerboard length.
In conventional fabrication of guitars, the neck member is often initially bowed or even twisted, if only slightly. Many of these faulty necks must be discarded. For some, adjustments can be made to properly position the fingerboard with respect to the strings. However, correction of subsequent rotational and/or lateral misalignments are very difficult where the fingerboard is not initially flat, and compensation is virtually impossible when attempted from the outset for an extreme bow or twisted neck structure.
It has been reported that as many as 60% of the carved wood neck components prepared in typical fabrication procedures are simply discarded where initial misalignment is detected. For example, even though an artisan may start with a piece of hard wood which is straight and true in its rough form, as sections of the hard wood are cut away to form the tapering neck body, existent stresses within the wood may cause its configuration to slightly bow or twist. Such misalignment is unacceptable in finer instruments and typically results in the component being discarded.
Even where the neck structure remains acceptable after initial tooling, when applied to the guitar and subjected to stringed forces of 175 to 200 pounds of compression, misalignment of the neck structure may result. Because of the unpredictable response of wood composition, guitar neck components cannot easily be prestressed to allow compensation for adjustments resulting from the described string pressure or loading which are imposed upon the neck.
Some adjustment has been facilitated by the use of a truss rod such as is illustrated in U.S. Pat. Nos. 3,396,621 and 4,557,174. The function of the truss rod is to redistribute loading forces imposed upon the neck to hopefully correct misalignment in the vertical bow which may occur with respect to the fingerboard and neck structure. It is important to note that the truss rod does not prevent loading of forces within the neck, but merely complements existing forces imposed by the strings with new forces to hopefully straighten or correct misalignment.
U.S. Pat. No. 4,432,267 illustrates a modular approach to providing for pre-strung adjustment in the neck component of the guitar by segmenting the neck and providing bolted attachment to the guitar body. Adjustment is accomplished by shifting the neck position with respect to the guitar body before tightening bolts which secure the neck to body orientation. This modular design has not provided the stability required for maintaining tuning nor for correcting other forms of misalignment. It is also cumbersome to adjust.
Furthermore, the prior problems of stress-imposed changes within the neck structure continue to be troublesome because forces arising from strings in tension can also affect distortion in the neck structure, particularly where weather conditions, heat and humidity might affect the wood. Therefore, a common impediment to construction and maintenance of a flat fingerboard and predictably straight neck body is the loading of the neck structure with the forces imposed by the tightly strung strings. Such stress is applied to the neck in conventional manner.
The disclosure of U.S. Pat. No. 3,251,257 ('257 patent) described the use of a rigid, metal bar for relieving string tension from the supporting neck and fingerboard structure. This disclosure explained that a rod could be inserted down a channel within the neck structure such that string tension applied at a distal end of the neck and fingerboard was loaded through the rigid bar into the guitar body. In this manner, the wood structure of the neck was not subjected to the severe tension and stress by reason of tightly drawn strings.
In addition, the '257 patent disclosed the use of a lifting force applied by contact of a threaded screw at the underside of the bar near the guitar body. For example, FIG. 2 of the '257 patent illustrates adjustment screw 39 which is mounted at a support plate 39' and has its distal end contacting within a notch at the underside of the bar. This permits tension to be applied at one side of the bar as the screw is rotated inward, thereby countering the tension applied to the strings 16. Accordingly, the '257 patent disclosed an adjustment mechanism which utilized the opposition of string tension versus bar tension in the vertical plane of the instrument to enable adjustment of the fingerboard and neck upward or downward. The limitations of such adjustment were controlled in part by the structural response of the neck material, the strings and string forces, and counter force established by the bar.
Although this mechanism provided improved adjustability along the vertical plane of the fingerboard, such adjustability was primarily limited to retracting the distal end of the fingerboard rearward by rotating the screw inward against the underside of the bar. Adjustments in the opposing direction were not as manageable because they depended upon the tension applied by the strings of the instrument. As guitar strings have become of lighter gauge, the difficulty of counter adjustments has increased. Furthermore, correction of misalignment was not possible without attachment of the strings. Therefore, modification of neck alignment at the manufacturer was limited.
In addition, the degree of abusive handling of instruments has greatly increased by virtue of modern performance styles, theatrics and attached hardware. For example, not only may a performance include swinging the guitar by its neck as part of performance choreography, but the use of tremolo bars and other hardware add greatly to the stress applied to the instrument, often resulting in misalignment of the fingerboard and neck structure.
An invention disclosed in U.S. Pat. No. 5,018,423 provides an adjustment mechanism for maintaining and/or correcting alignment of the fingerboard of a stringed instrument. Although this adjustment mechanism does not depend on string tension, some lateral adjustments require the support of the instrument body. Further, access to the adjustment mechanism is limited to entry from the back of the neck.
Although the collective approaches in the prior art have improved somewhat the state of the art in the field of stringed instruments, they are nonetheless fraught with disadvantages. Complete modularity of the neck member has still not been achieved, in that the neck member must be attached to the instrument body in order to be adjusted in all directions. This is because the adjustment mechanisms known in the art must be biased against the instrument body in order to impose displacement of the neck, at least in some directions. The pressure of the adjustment mechanism on the instrument body causes interior deformation in the instrument body, and the relative position of said adjustment mechanism and the body is often a source of unwanted vibration in the sound output of the instrument. Further, prior art adjustment mechanisms have not been accessible from the fingerboard side and have required that a hole be drilled in the back of the instrument body for access thereto. A further disadvantage is that adjusting the neck from the back side prevents the user from directly observing movement of the fretboard during the adjustment procedure.